What is the “tinting charge” added to the price of paint by the retailer?

For example, when customers want white Feelings Interior Paint, they can buy non-tinted Feelings Interior type A base paint. If they want some other colour, the paint shop’s tinting machine adds tinting paste and mixes it with types A or C base paint, and a tinting charge is added to the price. The amount depends on the tinting pastes used, retailer pricing policy, and so on. As the retailer aims to offer a virtually unlimited range of colours, the tinting charge is to cover the expenses incurred by machine investment, labour, and tinting pastes.